CHAIN WEIGHTED CPI

An alternative measurement for the Consumer Price Index (CPI), removing the biases associated with new products, changes in quality and discounted prices. The chain weighted CPI incorporates the average changes in the quantity of goods purchased, along with standard pricing effects. This allows the chain weighted CPI to reflect situations where customers shift the weight of their purchases from one area of spending to another.

The chain weighted CPI incorporates changes in both the quantities and prices of products. For example, let's examine clothing purchases between two years. Last year you bought a sweater for $40 and two t-shirts at $35 each. This year, two sweaters were purchased at $35 each and one t-shirt for $45.

Standard CPI calculations would produce an inflation level of 13.64%
((1 x 35 + 2 x 45)/ (1 x 40 + 2 x 35)) =1.1364

The chain weighted approach estimates inflation to be 4.55%
((2 x 35 + 1 x 45)/ (1 x 40 + 2 x 35)) =1.0455.

Using the chain weighted approach reveals the impact of a customer purchasing more sweaters than t-shirts.